This invention relates to a photosensitive composition. More particularly, it relates to high-resolution positive and negative photosensitive compositions suitable for the microlithography of semiconductor elements and to photoresist obtained from said composition.
In order to improve the performance of semiconductor elements such as integrated circuit (IC) and large scale integration (LSI), it is necessary to improve the resolution in fabrication. For this purpose a specially high resolution is required for the photoresist (photosensitive resist material) used in the working of semiconductor elements.
As one example of methods for working a semiconductor element with a high resolution in conformity with the requirement by using a conventional positive photoresist, there has been proposed a contrast enhancement method, in which a photobleaching material is coated on the positive photoresist to improve the contrast [ACS Polymer Preprints 26(2), 337 (1985)]. This method, however, has disadvantages in that a complicated process for working the element and an extended exposure time are necessary, and the like.
Further, as the conventional negative photoresist with high resolution, mention may be made of a composition comprising an aromatic azide compound and an alkali-soluble phenol-formaldehyde condensation resin in Japanese Patent Publication No. 22,082/70 and a composition comprising an aromatic azide compound and a hydroxystyrene polymer, which is disclosed in IEEE Transactions Electron Devices, vol. ED-28, No. 11, pp. 1306-1310 (1981). These photoresits, however, have their effective exposure wavelengths in an almost ultraviolet region. There is not known a negative photoresist sufficiently sensitive to the g-line (436 nm ray) of a mercury lamp, except for a photoresist described in SPIE Vol. 539, Advances in Resist Technology and Processing II pp. 189-193, (1985). Moreover, with respect to the wavelength of g-line there has never been obtained a photoresist high in both the sensitivity and the contrast. There is an additional problem in that it is far more difficult to synthesize an azide compound highly sensitive to g-line than to synthesize one sensitive to shorter wavelength light such as i-line (365 nm ray).